Vinyl silanes such as vinyl-tris(2-methoxyethoxy)silane are used as vulcanizing or crosslinking agents for natural and synthetic polymers. As a rule, the compositions are formulated by admixing the ingredients and compounding the resultant mixtures to a blend at elevated temperatures, below the vulcanization temperature or crosslinking temperature of the composition involved. It has been found, however, that vinyl silanes such as vinyl-tris(2-methoxyethoxy)silane, present in the polymeric compositions, undergo hydrolysis in the compounding step, yielding products which tend to be injurious to humans. Specifically, in the case of vinyl-tris(2-methoxyethoxy)silane, the silane hydrolyzes to 2-methoxyethanol, a volatile product which tends to be toxic to human beings.